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Let's say I have two active network connections that let me out to the internet.

I want certain applications to only use Network Connection 1, while some others should use Network Connection 2.

Is this possible in Windows XP? If so, how can it be done?

The main reason I wish to do this is I want to use a tethered phone's network for certain applications and an ethernet connection for others. Certain ports and networks are blocked by the ethernet connection, whereas they are not on my tethered phones connection.

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Well, usually, you should be able to specify which Nic use under each applications. Why do you want to use both network connections? I meaned, could you says a little bit more about your problem? – Dr I Nov 23 '09 at 18:46
This isn't generally possible, unless an application itself is specifically written to be aware of multiple NICs and lets the user specify. An example is most backup software, which many people want to run only on a dedicated network. Well - One way you can do what you're asking for is by running the different sets of applications in VMs, each corresponding to a given NIC - but that's probably a pain, especially on a laptop (which I assume you're using since you refer to tethering.) – mfinni Mar 5 '10 at 5:27

Static routes basically - you make it so that you can only talk to certain services/servers/networks via specific interfaces. Give us a lot more details and we'll help you but HERE is Microsoft's document of how to do it as a starter.

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This is to route specific network traffic to certain NICs, not applications. Example, say I want IE to try to access via NIC1 but I want firefox to access the same destination via NIC2. – snicker Nov 23 '09 at 18:53
Yeah I got that but I'm really not sure that's supported at all, hence my suggesting something that will work. – Chopper3 Nov 24 '09 at 9:19

I understood that your concern was about accessing some services that are blocked on the LAN through your mobile internet connection. If you're talking about only a few services you can try to get their ip address and configure static routes on your windows so that all ip packets aimed at these services go through your mobile phone. For example if you want to add a route to facebook, you can get its ip address with a ping and add a route with this dos command : route add gateway-ip.

Hope this helps

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The only thing that I think might work is using the built-in firewall, or, if it is not advanced enough, to install a better one. I know that the Windows Firewall allows you to specify rules based on applications. What you could do is then redirect traffic to a certain NIC based on the application.

If no firewall solution has rules like "redirect traffic from this app to this NIC", you can do another trick: install a proxy and have the firewall redirect (or NAT) your traffic to this proxy based on the application. You can have this proxy in a remote location and have a static route to it on the desired interface, or on your machine and configure the proxy to only use NICx.

All of the above is very theoretical, I never tried it, but it just might work.

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